Adrenal insufficiency in a neonatal foal.

A 3-day-old female Pinto was admitted with profuse watery diarrhea and severe hypovolemic shock. After 1 week of intensive care, the foal developed seizures associated with profound serum electrolyte abnormalities suggestive of hypoadrenocorticism. Treatment with prednisone and isotonic saline (0.9% NaCl) solution led to prompt clinical response. Premature withdrawal of prednisone resulted in relapse of clinical signs. A diagnosis of adrenal insufficiency was made on the basis of clinical signs, electrolyte abnormalities, low baseline cortisol concentration, and lack of response to administration of exogenous adrenocorticotropin. Two months later, adrenocortical function was normal and the foal was doing well clinically. Clinical signs of acute adrenal insufficiency in neonatal foals can be confused with other conditions, such as septicemia, enteritis, and ruptured urinary bladder. A persistently low serum sodium-to-potassium ratio associated with CNS malfunction should warrant investigation of adrenal gland function. Acute hypoadrenocorticism in foals may be reversible.